Technical Field
This disclosure relates to precision metrology, and more particularly to image acquisition systems such as machine vision inspection systems.
Description of the Related Art
Image acquisition systems such as precision machine vision inspection systems (or “vision systems” for short) may be used for precise measurements of objects and to inspect other object characteristics. Such systems may include a computer, camera, optical system, and a stage that moves to allow workpiece traversal. One exemplary system, characterized as a general-purpose “off-line” precision vision system, is the QUICK VISION® series of PC-based vision systems and QVPAK® software available from Mitutoyo America Corporation (MAC), located in Aurora, Ill. The features and operation of the QUICK VISION® series of vision systems and the QVPAK® software are generally described, for example, in the QVPAK 3D CNC Vision Measuring Machine User's Guide, published January 2003, which is hereby incorporated by reference in its entirety. This type of system uses a microscope-type optical system and moves the stage to provide inspection images of small or large workpieces at various magnifications.
In various applications, it is desirable to perform high-speed autofocus and/or other operations to facilitate high-speed measurements for high throughput in either stationary or non-stop moving inspection systems. The speed of autofocus and other operations requiring focusing in conventional machine vision inspection systems is limited by the motion of the camera through a range of Z-height positions. There is a need for improved autofocus and/or other operations utilizing alternative methods of collecting images at a high speed without compromising image quality and/or dimensional accuracy in the images.